Keeping Our Promises Act This bill expands the list of diseases that are provided a presumption of service-connection for veterans who served in the Republic of Vietnam between January 9, 1962, and May 7, 1975. The bill extends through September 30, 2030, the requirement for the Department of Veterans Affairs (VA) to make determinations and submissions related to the connection between herbicide exposure and occurrence of disease. Additionally, the VA is prohibited from taking the costs of compensation into account when determining the association between exposure to an herbicide agent and occurrence of a disease. The bill requires the VA to determine within 120 days (currently 60) whether a presumption of service-connection is warranted for diseases covered by a National Academy of Sciences report.